Specifications

Operating System Routines
IOC$ALOXBIMAPRM, IOC$ALOXBIMAPRMN
Description
IOC$ALOXBIMAPRM and IOC$ALOXBIMAPRMN permanently allocate a
contiguous set of XBI+ map registers and record the allocation in the ADP and
CRB. These routines differ in the way in which they determine the number and
location of the map registers they allocate:
• IOC$ALOXBIMAPRM calculates the number of map registers required using
the values contained in UCB$W_BCNT and UCB$W_BOFF.
• IOC$ALOXBIMAPRMN uses the value in R3 as the number of required
registers.
If an odd number of map registers is required, these routines round up this value
to an even multiple of 64. The routines then search for the required number of
map registers, returning SS$_NORMAL when they are found. If there are not
enough contiguous XBI+ map registers available, the routines return an error
status indicator (SS$_INSFMAPREG).
Once XBI+ map registers have been permanently allocated to the controller,
subsequent calls to IOC$ALOXBIMAPRM and IOC$ALOXBIMAPRMN will
return a success status indicator (SS$_NORMAL) without allocating additional
map registers.
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